Promoters for controlling acidity and pore size of zeolite catalysts for use in alkylation

ABSTRACT

A metal-modified alkylation catalyst including a metalizeolite is provided where the metal is one or two selected from the group consisting of yttrium and a rare earth of the lanthanide series other than cerium. Where two metals are used, one may be Ce or La. The metal-promoted zeolite is useful as a molecular sieve aromatic alkylation catalyst for the production of ethylbenzene by the ethylation of benzene in the liquid phase or critical phase. An alkylation product is produced containing ethylbenzene as a primary product with the attendant production of heavier alkylated by-products of no more than 10-60 wt % of the ethylbenzene.

FIELD OF THE INVENTION

The present invention is related in one non-limiting embodiment tometal-modified alkylation catalysts, and relates more particularly toanother non-limiting embodiment to metal/beta zeolite catalysts usefulin the alkylation of an aromatic substrate in the liquid phase by a lowmolecular weight alkylating agent.

BACKGROUND OF THE INVENTION

The alkylation of benzene with ethylene over a molecular sieve catalystis a well-known procedure for the production of ethylbenzene. Typically,the alkylation reaction is carried out in a multistage reactor involvingthe interstage injection of ethylene and benzene to produce an outputfrom the reactor that involves a mixture of monoalkyl andpolyalkylbenzene. The principal monoalkylbenzene is, of course, thedesired ethylbenzene product. Polyalkylbenzenes include diethylbenzene,triethylbenzene, and xylenes.

In many cases, it is desirable to operate the alkylation reactor inconjunction with the operation of a transalkylation reactor in order toproduce additional ethylbenzene through the transalkylation reaction ofpolyethylbenzene with benzene. The alkylation reactor can be connectedto the transalkylation reactor in a flow scheme involving one or moreintermediate separation stages for the recovery of ethylene,ethylbenzene, and polyethylbenzene.

Transalkylation may also occur in the initial alkylation reactor. Inthis respect, the injection of ethylene and benzene between stages inthe alkylation reactor not only results in additional ethylbenzeneproduction but also promotes transalkylation within the alkylationreactor in which benzene and diethylbenzene react through adisproportionation reaction to produce ethylbenzene.

Various phase conditions may be employed in the alkylation andtransalkylation reactors. Typically, the transalkylation reactor will beoperated under liquid phase conditions, i.e., conditions in which thebenzene and polyethylbenzene are in the liquid phase, and the alkylationreactor is operated under gas phase conditions, i.e., pressure andtemperature conditions in which the benzene is in the gas phase.However, liquid phase or critical phase conditions can be used where itis desired to minimize the yield of undesirable by-products from thealkylation reactor.

It is a continuing goal of the industry to find and use catalysts thatgive improved activity and selectivity.

SUMMARY OF THE INVENTION

There is provided, in one form, a molecular sieve catalyst concerning azeolite promoted with a promoter where the promoter can be one ionselected from the group consisting of yttrium and a rare earth of thelanthanide series other than cerium. Alternatively, the promoter may betwo ions where the first ion is yttrium or a rare earth of thelanthanide series other than cerium and the second, different ion islanthanum, cerium, yttrium or a rare earth of the lanthanide series. Itshould be understood herein that the term “promoter” also includes acounterion.

There is additionally provided in another non-limiting embodiment amolecular sieve catalyst that involves a zeolite formed with a binderpromoted with a promoter that may be one ion which may be yttrium or arare earth of the lanthanide series other than cerium. Alternatively thepromoter may be two ions where the first ion is yttrium or a rare earthof the lanthanide series other than cerium and the second, different ionis lanthanum, cerium, yttrium or a rare earth of the lanthanide serieswhere the promoter ion/aluminum atomic ratio is within the range of fromabout 0.1 to about 10. Further, the catalyst additionally includes thebinder.

In another embodiment, there is provided a process for preparing amolecular sieve catalyst that includes synthesizing a zeolite byhydrothermally digesting a reaction mixture comprising silica, alumina,an alkali metal oxide and an organic templating agent. The synthesizedzeolite is treated at least once with an ion-exchange medium to exchangea portion of the active sites in the zeolite with the alkali metal.Further, the ion-exchanged zeolite may be calcined at least once. One ortwo metals are incorporated into the zeolite system by treating theion-exchanged zeolite with an ion-exchange medium that includes a metalsalt solution to obtain a metal/zeolite. The metal may be one metal thatis yttrium or a rare earth of the lanthanide series other than cerium.Alternatively, the metal component may actually be two metals where thefirst metal is yttrium or a rare earth of the lanthanide series otherthan cerium and the second, different metal is lanthanum, cerium,yttrium and a rare earth of the lanthanide series. The metal/zeolite isfixed with a binder to produce a mulled metalizeolite binder mixture.The metal/zeolite binder mixture is pelletized and the resulting pelletsare dried.

In a different non-limiting embodiment there is provided a process foralkylation of an aromatic compound that involves supplying an aromaticfeedstock into a reaction zone and into contact with a metal-promotedzeolite molecular sieve alkylation catalyst in the reaction zone. Thecatalyst contains metal in an amount to provide a metal/aluminum atomicratio within the range of about 0.1 to about 10. The metal may be justone metal that is yttrium or a rare earth of the lanthanide series otherthan cerium. Alternatively, the metal may be two metals where the firstmetal yttrium or a rare earth of the lanthanide series other than ceriumand the second, different metal is lanthanum, cerium, yttrium or a rareearth of the lanthanide series. A C₂-C₄ alkylating agent is supplied tothe reaction zone in an amount to provide an aromaticcompound/alkylating agent mole ratio in the range of about 1 to about 30inclusive. The reaction zone is operated at temperature and pressureconditions in which the aromatic compound is in the supercritical orliquid phase to cause alkylation of the aromatic compound in thepresence of the zeolite alkylation catalyst to give an alkylationproduct as a primary product with the attendant production of heavieralkylated by-products in a minor amount. The alkylation product isrecovered from the reaction zone.

In yet another non-restrictive embodiment there is provided a processfor the production of ethylbenzene that includes providing an alkylationreaction zone. The reaction zone contains a metal-promoted zeolitearomatic alkylation catalyst. The metal in the catalyst may be one metalthat is yttrium or a rare earth of the lanthanide series other thancerium. Alternatively, the metal may be two metals where the first metalis yttrium or a rare earth of the lanthanide series other than ceriumand the second, different metal is lanthanum, cerium, yttrium or a rareearth of the lanthanide series. A feedstock containing at least 20%benzene is co-mingled with a stream containing at least 10% ethylene andsupplied to the alkylation reaction zone. The alkylation reaction zoneis operated at temperature and pressure conditions in which benzene isin the supercritical phase or liquid phase to cause ethylation of thebenzene in the presence of the promoted zeolite alkylation catalyst toproduce an alkylation product that includes a mixture of benzene,ethylbenzene, and polyethyl benzene. The alkylation product is recoveredfrom the alkylation reaction zone and the product from the alkylationreaction zone is supplied to a recovery zone for the separation andrecovery of ethylbenzene from the alkylation product and the separationand recovery of a polyalkylated aromatic component that includesdiethylbenzene. At least a portion of the polyalkylated aromaticcomponent including diethylbenzene in the polyalkylated aromaticcomponent is supplied to a transalkylation reaction zone that contains amolecular sieve transalkylation catalyst. Benzene is supplied to thetransalkylation reaction zone, and the transalkylation reaction zone isoperated under temperature and pressure conditions to causedisproportionation of the polyalkylated aromatic fraction to produce adisproportionation product having a reduced diethylbenzene content andan enhanced ethylbenzene content.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an idealized schematic block diagram of analkylation/transalkylation process embodying one non-limiting embodimentof the process.

DETAILED DESCRIPTION OF THE INVENTION

Cerium has been shown to be superior to lanthanum when used for criticalphase alkylation processes. Although both ions possess the same charge,there have been significant differences in activity and selectivity.Attention is respectfully directed to U.S. Pat. No. 6,933,418 filed Oct.4, 2002 and U.S. Pat. No. 6,987,078 filed Oct. 3, 2003, both of whichare incorporated herein in their entirety. Without wishing to be limitedto any explanation or theory, it may be that the size of the ion and itsacidity could be influential in the alkylation process. Aciditygenerally increases for these ions as they move to the right along thePeriodic Table from lanthanum. Further, those factors could be adjustedwith the choice of promoter applied to the zeolite. One importantfeature is to balance the acidity and the ion size to get optimumresults in activity and selectivity. Ion size is thought to affectmolecular traffic in and out of the pores of the catalysts.

For example, yttrium (Y) has the same ionic structure as cerium (Ce),although one less orbital is full. It would be a smaller and moreelectropositive ion than Ce. In addition, other elements in thelanthanide series have the same charge as Ce when ionized, but will besmaller and more electropositive as their position on the Periodic Tablemoves to the right. One potential promoter might be neodymium (Nd). Itsion is smaller and more electropositive than Ce. Other elements in thelanthanide series may be used to fine-tune their role as promoters. Itis expected that only one or two metals will be used in the catalysts,rather than a wide mixture of lanthanides. Thus, in the case where onlyone promoter is used, the promoter should be yttrium or a member of thelanthanide series other than Ce. In the case where two promoters areused, the first promoter should be yttrium or a member of the lanthanideseries other than Ce, and the second promoter should be different thanthe first, but may be La or Ce or from the same group as the firstpromoter.

In one non-limiting embodiment, the zeolite has a promoter ion/aluminumatomic ratio ranging from about 0.1/1 to about 2.5/1 relative to thealuminum in the zeolite. (All stated ranges herein are inclusive of theend points unless otherwise noted.) In another non-restrictiveembodiment, the ratio of promoter ion to aluminum atomic ratio rangesfrom about 0.5 to about 1.25.

The molecular sieve catalyst employed in the critical phase alkylationreactor is a zeolite catalyst that can be a conventional zeolitemodified by the inclusion of a metal as described below. For thealkylation of this method it is expected that any zeolite may be used.In one non-restrictive embodiment, zeolite Beta is employed. Themetal-promoted zeolite catalyst will normally be formulated in extrudatepellets of a size of about ⅛-inch or less (0.32 cm or less), employing abinder such as silica or alumina. In one non-limiting embodiment, thebinder is silica, which results in catalysts having somewhat enhanceddeactivation and regeneration characteristics than zeolite formulatedwith a conventional alumina binder. Typical catalyst formulations mayinclude about 20 wt % binder and about 80 wt % molecular sieve. Thecatalyst employed in a transalkylation reactor normally will take theform of a zeolite Y catalyst, such as zeolite Y or ultra-stable zeoliteY. Various zeolites of the Y and beta types are in themselves well knownin the art. For example, zeolite Y is disclosed in U.S. Pat. No.4,185,040 to Ward, and zeolite beta is disclosed in U.S. Pat. No.3,308,069 to Wadlinger and U.S. Pat. No. 4,642,226 to Calvert et al.,all of which are incorporated by reference herein.

The metal-promoted zeolite employed in the alkylation reactor can be azeolite of the type described in Wadlinger or Calvert, which has beenmodified by the inclusion of the metal in the crystalline framework. Themetal-promoted zeolite employed can be based on a high silica/aluminaratio zeolite or a ZSM-12 modified zeolite as described. As mentioned,the metal is one or possibly two metals that are from the group ofyttrium and a rare earth of the lanthanide series other than cerium.When two metals are used, one of them may be La or Ce.

Basic procedures for the preparation of zeolite are well known to thoseskilled in the art. Such procedures are disclosed in the aforementionedU.S. Pat. No. 3,308,069 to Wadlinger et al. and U.S. Pat. No. 4,642,226to Calvert et al. and European Patent Publication No. 159,846 to Reuben,the disclosures of which are incorporated herein by reference in theirentirety. The zeolite can be prepared to have a low sodium content, i.e.less than 0.2 wt. % expressed as Na₂O and the sodium content can befurther reduced to a value of about 0.02 wt. % by an ion exchangetreatment.

As disclosed in the above-referenced U.S. patents to Wadlinger et al.,and Calvert et al., zeolite may be produced by the hydrothermaldigestion of a reaction mixture comprising silica, alumina, sodium orother alkyl metal oxide, and an organic templating agent. Typicaldigestion conditions include temperatures ranging from slightly belowthe boiling point of water at atmospheric pressure to about 170° C. atpressures equal to or greater than the vapor pressure of water at thetemperature involved. The reaction mixture is subjected to mildagitation for periods ranging from about one day to several months toachieve the desired degree of crystallization to form the zeolite.Unless steps are taken to minimize the alumina content, the resultingzeolite is normally characterized by a silica to alumina molar ratio(expressed as SiO₂/Al₂O₃) of between about 20 and about 500. In analternate non-limiting embodiment the ratio is between about 50 to about250.

The zeolite is then subjected to ion exchange with ammonium ions atuncontrolled pH. In one non-limiting embodiment, an aqueous solution ofan inorganic ammonium salt, e.g., ammonium nitrate, is employed as theion-exchange medium. Following the ammonium ion-exchange treatment, thezeolite is filtered, washed and dried, and then calcined at atemperature between about 530° C. and 580° C. for a period of two ormore hours.

The zeolite can be characterized by its crystal structure symmetry andby its x-ray diffraction patterns. In a non-limiting example, zeolitebeta is a molecular sieve of medium pore size, about 5-6 angstroms, andcontains 12-ring channel systems. Zeolite beta is of tetragonal symmetryP4₁22, where a=12.7, c=26.4 Å (W. M. Meier and D. H. Olson Butterworth,Atlas of Zeolite Structure Types, Heinemann, 1992, p. 58); ZSM-12 isgenerally characterized by monoclinic symmetry. The pores of zeolitebeta are generally circular along the 001 plane with a diameter of about5.5 angstroms and are elliptical along the 100 plane with diameters ofabout 6.5 and 7.6 angstroms. Zeolite beta is further described inHiggins et al, “The Framework Topology of Zeolite Beta,” Zeolites, 1988,Vol. 8, November, pp. 446452, the entire disclosure of which isincorporated herein by reference.

The procedure disclosed in EP 507,761 A1 to Shamshoum, et al. forincorporation of lanthanum into zeolite beta can be employed to producethe metal promoted zeolite beta used in the present process. Thus,corresponding metal nitrates or other salts may be dissolved indeionized water and then added to a suspension of zeolite beta indeionized water following the protocol disclosed in EP 507,761 A1 forthe incorporation of lanthanum into zeolite beta by ion exchange.Following the ion exchange procedure, the metal exchanged zeolite betacan then be filtered from solution washed with deionized water and thendried at a temperature of 110° C. The powdered metal exchanged zeolitebeta can then be mulled with an aluminum or silicon binding agentfollowed by extrusion into pellet form. Other, known procedures may alsobe used to prepare these zeolites.

The process also involves the liquid phase or critical phase alkylationof benzene over a metal-promoted zeolite alkylation catalyst underconditions to control and desirably minimize the yield of by-products inthe alkylation reaction zone. It will be appreciated that although thisembodiment is described in terms of alkylating benzene with ethylene asan alkylating agent that the process could also be applied to thealkylation of other aromatic feedstocks using lower alkylating agentssuch as C₂-C₄ alkylating agents, with appropriate adjustments.

The feedstock supplied to the alkylation reaction zone comprises benzeneand ethylene. Typically, the benzene and ethylene streams will becombined to provide a benzene-ethylene mixture into the reaction zone.The benzene stream, which is mixed with the ethylene either before orafter introduction into the reaction zone, should be a relatively purestream containing only very small amounts of contaminants. In onenon-limiting embodiment, the benzene stream may contain at least 90 wt %benzene. Alternatively, the benzene stream will be at least 98 wt %benzene with only trace amounts of such materials as toluene,ethylbenzene, and C₇ aliphatic compounds that cannot readily beseparated from benzene.

However, it is also possible for the alkylation to be conducted withdilute benzene or dilute ethylene. In such cases, suitable diluents mayinclude, but are not necessarily limited to, ethane, mixed hexanes,mixed butanes, and the like. By the term “dilute” is meant that theethylene may be present in a ratio with the diluent of about 8/1 orless. The same definition applies with respect to dilute benzene exceptthe ratio of benzene to diluent is less than 8/1. In anothernon-restrictive version of the process, the reactant may be present in aratio of about 1/10 or less.

The alkylation reaction may be conducted in the liquid phase at apressure well above the vapor pressure of the aromatic substrate at thereaction temperature involved to ensure that a liquid phase ismaintained in the reaction zone. In the liquid phase, the pressures mayrange from about 425 to about 600 psia (about 2.9 to about 4.1 MPa), inanother non-limiting embodiment from about 450 to about 550 psia (about3.1 to about 3.8 MPa). The temperature may range from about 175 to about300° C., alternatively from about 200 to about 250° C. The mole ratio ofaromatic compound to alkylating agent may range from about 1 to about 30in one non-limiting embodiment, and in an alternate, non-restrictiveversion may range from about 1 to about 25. The liquid phase reactionmay be performed in a flooded bed format, a staged reaction format, orother suitable procedure.

The alkylation reaction zone may be also operated under supercriticalconditions, that is, pressure and temperature conditions which are abovethe critical pressure and critical temperature of benzene. Specifically,the temperature in the alkylation zone is at or above about 280° C., andthe pressure is at or above about 650 psia (about 4.5 MPa). In anothernon-limiting embodiment, the temperature in the alkylation reactor willbe maintained at an average value within the range of about 280 to about350° C., alternatively from about 320 to about 380° C. and a pressurewithin the range of about 650 to about 975 psia (about 4.5 to about 6.7MPa), in another non-restrictive embodiment from about 550 to about 850psia (about 3.8 to about 5.9 MPa). If desired, higher alkylationtemperatures can be employed since the metal-promoted zeolite retainsits structural integrity at temperatures of about 530-540° C. Zeolitewhich has not been promoted with a metal may lose its structuralintegrity as the temperature reaches about 500° C. The critical phasealkylation reaction is exothermic with a positive temperature gradientfrom the inlet to the outlet of the reactor, the temperature increasebeing determined by the ratio of benzene to ethylene.

The operation of the alkylation reaction zone in the supercriticalregion enables the alkylation zone to be operated under conditions inwhich the benzene-ethylene mole ratio can be maintained at relativelylow levels, usually some-what lower than the benzene-ethylene mole ratioencountered when the alkylation reaction zone is operated under liquidphase conditions. In most cases, the benzene-ethylene mole ratio will bewithin the range of about 1-15. In another non-limiting embodiment, thebenzene mole ratio will be maintained during at least part of a cycle ofoperation at a level within the lower end of this range, specifically,at a benzene-ethylene mole ratio of less than about 10. Abenzene-ethylene mole ratio within the range of 3-8 may be employed withadequate cooling of the reactor. Thus, operation in the supercriticalphase offers the advantages of gas phase alkylation in which thebenzene-ethylene ratio can be kept low but without the problemsassociated with by-product formation, specifically xylene formation,often encountered in gas-phase alkylation. At the same time, operationin the super critical phase offers the advantages accruing to liquidphase alkylation in which the by-product yield is controlled to lowlevels. The pressures required for operation in the super critical phaseare not substantially greater than those required in liquid phasealkylation, and the benzene in the supercritical phase functions as asolvent to keep the zeolite catalyst clean and to retard coking leadingto deactivation of the catalyst. However, it should be understood thatliquid phase conditions can be used with this process.

As indicated by the experimental work described later, themetal-promoted zeolite enables super critical phase alkylation to becarried out with by-products that are expected to be substantially lessthan the corresponding by-products produced with super critical phasealkylation employing lanthanum-promoted beta zeolite of similar orgreater content. Thus, the alkylation reaction zone can be operated atsuper critical phase temperature and pressure conditions to provide acomposite by-product yield of propylbenzene and butylbenzene which isless than the corresponding composite by-product yield of propylbenzeneand butylbenzene for a corresponding beta zeolite catalyst promoted withlanthanum at a lanthanum/beta atomic ratio at least as great as themetal/aluminum atomic ratio of the metal-promoted zeolite. In onenon-limiting embodiment, the alkylation reaction zone is operated attemperature and pressure conditions to provide a composite product yieldof propylbenzene and butylbenzene which is no more than one-half of thecorresponding composite by-product yield of propylbenzene andbutylbenzene produced with the lanthanum-promoted zeolite beta. Inanother non-limiting embodiment, the composite product yield ofpropylbenzene and butylbenzene is no more than that of the correspondingcomposite by-product yield of propylbenzene and butylbenzene producedwith the lanthanum-promoted zeolite beta. The same advantages areexpected to be present when the reaction is conducted under liquid phaseconditions.

Turning now to FIG. 1, there is illustrated a schematic block diagram ofan alkylation/transalkylation process employing one or more of theinnovations described herein. As shown in FIG. 1, a product streamcomprising a mixture of ethylene and benzene in a mole ratio of benzeneto ethylene of about 1 to 30 is supplied via line 1 through a heatexchanger 2 to an alkylation reaction zone 4. Alkylation zone 4 in onenon-limiting embodiment comprises one or more multi-stage reactorshaving a plurality of series-connected catalyst beds containing ametal-modified zeolite alkylation catalyst as described herein. Thealkylation zone 4 is operated at temperature and pressure conditions tomaintain the alkylation reaction in the liquid or supercritical phase,i.e. the benzene is in the liquid or supercritical state, and at a feedrate to provide a space velocity enhancing diethylbenzene productionwhile retarding by-products production. In another non-limitingembodiment, the space velocity of the benzene feed stream will be withinthe range of 1-150 hrs⁻¹ LHSV per bed.

The output from the alkylation reactor 4 is supplied via line 5 to anintermediate benzene separation zone 6 that may take the form of one ormore distillation columns. Benzene is recovered through line 8 andrecycled through line 1 to the alkylation reactor 4. The bottomsfraction from the benzene separation zone 6, which includes ethylbenzeneand polyalkylated benzenes including polyethylbenzene, is supplied vialine 9 to an ethylbenzene separation zone 10. The ethylbenzeneseparation zone 10 may likewise involve one or more sequentiallyconnected distillation columns. The ethylbenzene is recovered throughline 12 and applied for any suitable purpose, such as in the productionof vinyl benzene. The bottoms fraction from the ethylbenzene separationzone 10, which comprises polyethylbenzene, principally diethylbenzene,is supplied via line 14 to a transalkylation reactor 16. Benzene issupplied to the transalkylation reaction zone through line 18. Thetransalkylation reactor 16, which in one non-limiting embodiment isoperated under liquid phase conditions, contains a molecular sievecatalyst, in one non-limiting embodiment zeolite-Y, which has a somewhatlarger pore size than the metal-modified zeolite used in the reactionalkylation zone. The output from the transalkylation reaction zone 16 isrecycled via line 20 to the benzene separation zone 6.

It will be appreciated that the process herein may be used inconjunction with parallel-connected alkylation and transalkylationreactors with multi-stage recovery zones for separating and recycling ofcomponents. Such systems are described in U.S. Pat. No. 6,933,418 toKevin P. Kelly, et al., which is incorporated herein by reference in itsentirety.

The catalysts and processes will now be further discussed with respectto certain more specific Examples which are provided merely to furtherillustrate the innovations previously discussed and not to limit them inany way.

EXAMPLE 1

A beta zeolite catalyst would be prepared by employing a multiple ionexchange and calcinations procedures as described previously. The betazeolite may have a silica/aluminum ratio of about 25 (within the rangeof about 20 to 500), and contain tetraethylammonium hydroxide as aretained templating agent, and may have an initial surface area of 210m²/g and a sodium content of about 0.5 to 1% Na₂O after calcination. Theinitial ammonium ion exchange treatment may be done by submersing thecalcined zeolite catalyst in an aqueous solution of ammonium nitratehaving a normality of 2 at a zeolite to ammonium nitrate ratio of about2:3. The zeolite beta may be submersed in the ion exchange medium undermild agitation at 85° C. for a period of two hours. The beta zeolite maythen be filtered and dried. The dried powder may be calcined atprogrammable temperature to a maximum of 570° C. convert the zeolite tothe hydrogen form. This calcined powder would then be ion-exchanged withammonium ions in a similar manner as described above. Alternatively, itshould be appreciated that commercial zeolites may be acquired to makethe catalysts.

The metal as defined herein may then be incorporated into the zeolitesystem by an ion exchange method. In a non-restrictive instance, 80grams of anhydrous NH₄/beta zeolite may be suspended in deionized water.A salt solution of metal nitrate may be prepared by dissolving 1.247grams of M(NO₃)₃ in deionized water. This salt solution may be slowlyadded to the zeolite suspension at a temperature of about 90° C. Theexchange may be continued for about 3 hours. The metal exchanged zeolitemay be filtered, washed and dried at 110° C. The chemical analysis ofthis powder form (metal/NH₄ beta-zeolite could be as given below inTable I, and may show a metal content of about 0.1 wt %.

TABLE I Chemical Analysis (anhydrous basis) of Metal/beta Zeolite Wt %Sample Si Al Metal Na* K* SiO₂/Al₂O₃ Metal/NH₄ beta 43.2 2.7 0.12 0 030.9 *<0.01%

The powdered metal/beta zeolite (e.g. 66.7 g, anhydrous basis) may bemulled with nitric acid-treated alumina (for instance 21.9 g, anhydrousbasis) and extruded into 1/16 inch pellets. (0.16 cm). The resultingextruded zeolite pellets may then be calcined in an oven under air in aprogrammed temperature, up to a maximum of about 530° C. The metal/NH₄beta catalyst could thus be converted into a metal oxide/H-beta catalystas the ammonia evolved [NH⁴⁺→NH³⁺H⁺] during calcinations of theextrudates at 530° C. The final catalyst may have the physicalproperties given in Table II.

TABLE II Properties Expected for an Example I Catalyst Surface Area609.1 m²/g Micropore Area 325.0 m²/g Pore Volume 0.13 ml/g Average PoreDiameter 33.1 Å

EXAMPLE 2

In experimental work, alkylation reactor runs would be carried outemploying a single stage alkylation reactor. The reactor would beoperated as a laboratory simulation of a single stage of a multiplestage reactor that would be used commercially. In carrying out theexperimental work, a metal-promoted beta zeolite having a silica/aluminaratio of about 150 and a metal/aluminum atomic ratio of 0.75 would beemployed. This catalyst would be formed employing a silica binder asdescribed previously. Comparative experimental work carried out woulduse a lanthanum-promoted beta zeolite catalyst, also having a silicaalumina ratio of 150 and having a lanthanum/aluminum atomic ratio of 1.0formulated with a silica binder.

The metal-promoted beta zeolite would be used in the alkylation reactorthrough five (5) regenerations for a total cumulative time of in excessof 140 days. Throughout the successive runs the inlet temperature of thereactor would be about 300° C.±5° C. and the temperature at the outletof the reactor would be about 350° C.±10° C., resulting in anincremental temperature increase across the reactor of about 40-50° C.The reactor would be operated at an inlet pressure of about 600 psig(4.1 MPa) with a pressure gradient across the reactor of only a fewpounds per square inch. These conditions are more representative of nearcritical phase alkylation, but it should be understood that thecatalysts can be employed in the liquid phase as well.

The lanthanum promoted zeolite beta would be employed in a test runspanning about 55 days on line with regeneration of the catalyst at theconclusion of 20 days. The lanthanum promoted zeolite beta may have asilica alumina ratio of 150 and a lanthanum/aluminum atomic ratio of1.0. Generally, a regeneration procedure may involve injecting anoxygen-containing gas into the reaction zone to provide a regenerationtemperature in the reaction zone of between about 500 and about 585° C.

EXAMPLE 3

This Example illustrates how use of dilute ethylene to alkylate benzeneto ethylbenzene could be performed using mixed hexanes as the diluentfor ethylene in place of ethane. The mixed hexanes did not undergo anysubstantial conversion in the reactor. The reaction could be runaccording to the conditions outlined in Table III

TABLE III Benzene:ethylene = molar 10:1 molar LHSV benzene 10 hr⁻¹Ethylene rate 83 ml/min STP Pressure 750 psig (5.2 MPa) Feed 12,500 ghexane 28,400 g benzene Ethylene/diluent vol/vol 20/80 Diluent Mixedhexanes Temperature 290° C. before ethylene addition Catalyst volume 20ml

Mixed hexanes may be used as a diluent in lieu of diluting ethylene withethane. The hexanes were added as a mixture of branched isomers, many ofwhich contained tertiary hydrogen that could react to create sideproducts.

The test could be run for four days. After the first day, the ethylenemay be added to the reactor. For this work, it is expected that allethylene added to the reactor would consumed, and that there would be nogas in the effluent.

In such a test, as in all the experiments conducted in the criticalphase, no xylenes would be expected to be produced. It would be expectedthat analysis by mass spec would show trace amounts of many differentbranched substituted benzene compounds in the effluent. These would bereported as unknowns/heavies. Since the heavies would be reported as ppmrelative to ethylbenzene and there would be expected to resultconsiderably more hexane than ethylbenzene in the effluent, only a smallamount of isomers have to be converted to produce the heavies. Theseresults would suggest that dilute ethylene could be used successfully toalkylate benzene to ethylbenzene. As such, it creates opportunities forobtaining alternate supplies of ethylene that could favor the use ofcritical phase technology economically. The results would also show thatdilute benzene could be used as the substrate to perform the alkylationreaction.

It is expected that the ethyl benzene yield in terms of percentconversion, and that the by-product yield (e.g. propylbenzene andbutylbenzene), relative to ethyl benzene, would be substantially betterthan the corresponding values observed for the lanthanum-promoted betazeolite. This is because yttrium ion and the lanthanide ions are smallerand more electropositive than lanthanum, or cerium, for that matter. Themetals of described herein would be expected to provide more selectivityand activity than lanthanum. As noted, generally the elements are moreacidic and more electropositive going to the right on the Periodic Tablefrom lanthanum.

The metal beta alkylation catalyst would be expected to showsubstantially lower by-products yield in each of the three (3)categories (propylbenzenes, butylbenzenes and heavies) as compared withlanthanum-promoted beta zeolite, and also as compared withcerium-promoted beta zeolite. Specifically, the composite by-productyield of propylbenzene and butylbenzene produced during super criticalphase or liquid phase alkylation over the metal-promoted zeolite wouldbe expected to be less than one-half of the corresponding by-productyield of propylbenzene and butylbenzene observed for thelanthanum-promoted zeolite. The data for the metal-promoted betazeolites would be expected to show consistent results even after aseries of regenerations.

Of course, the alkylation methods discussed herein are intended to beapplied in a production-scale alkylation plant to produce large,commercial quantities of product, e.g. ethylbenzene.

In the foregoing specification, the catalysts and processes have beendescribed with reference to specific embodiments thereof, and has beendemonstrated as effective in providing methods for preparing alkylatedaromatics, particularly ethylbenzene. However, it will be evident thatvarious modifications and changes can be made to the method withoutdeparting from the broader spirit or scope of the innovations as setforth in the appended claims. Accordingly, the specification is to beregarded in an illustrative rather than a restrictive sense. Forexample, specific promoter-modified zeolites, aromatic compounds,alkylating agents, and other components falling within the claimedparameters, but not specifically identified or tried in a particularcatalyst preparation method, are anticipated and expected to be withinthe scope of this invention. Further, the process of producing alkylatedaromatic products can be conducted under conditions (temperature,pressure, feed rates, etc.) other than those exemplified herein.

1. A process for alkylation of an aromatic compound comprising:supplying an aromatic feedstock comprised of benzene into a reactionzone and into contact with a catalyst consisting essentially of ametal-promoted beta zeolite molecular sieve alkylation catalyst in areaction zone, wherein said catalyst contains metal in an amount toprovide a metal/aluminum atomic ratio within a range of about 0.1 toabout 10, where the metal is selected from the group consisting ofyttrium, cerium, and a rare earth of the lanthanide series other thanlanthanum; supplying a C₂-C₄ alkylating agent to the reaction zone in anamount to provide an aromatic compound/alkylating agent mole ratio inthe range of about 1 to about 30 inclusive; operating the reaction zoneat temperature and pressure conditions in which the aromatic compound isin a supercritical or liquid phase to cause alkylation of the aromaticcompound in the presence of the zeolite alkylation catalyst to producean alkylation product comprised of ethylbenzene as a primary productwith an attendant production of heavier alkylated by-products in a minoramount; and recovering the alkylation product from the reaction zone,wherein a total by-product yield for the metal promoted zeolite is lessthan a total by-product yield under the same temperature and pressureconditions for a zeolite promoted with lanthanum at a lanthanum/aluminumatomic ratio at least equal to the metal/aluminum atomic ratio of themetal-promoted zeolite catalyst.
 2. The process of claim 1 where thealkylating agent comprises ethylene.
 3. The process of claim 2 where thereaction zone is operated in supercritical phase and the benzene toethylene mole ratio is less than about
 10. 4. The process of claim 2where the reaction zone is operated in liquid phase and the benzene toethylene mole ratio is within a range of from about 1 to about
 30. 5.The process of claim 2 wherein the zeolite has a silica/alumina moleratio within a range of from about 50 to about
 150. 6. The process ofclaim 2 wherein the zeolite has a metal-aluminum atomic ratio is withina range of from about 0.1 to about
 10. 7. The process of claim 1 whereinthe alkylation zone is operated at temperature and pressure conditionsto provide a total by-product yield of propylbenzene and butylbenzenewhich is less than a corresponding total by-product yield ofpropylbenzene and butylbenzene for a zeolite promoted with lanthanum ata lanthanum/aluminum atomic ratio at least equal to a metal/aluminumatomic ratio of the metal-promoted zeolite catalyst under the sametemperature and pressure conditions.
 8. The process of claim 1 whereinthe alkylation reaction zone is operated at temperature and pressureconditions to provide a total by-product yield of propylbenzene andbutylbenzene which is no more than one-half of a correspondingby-product yield of propylbenzene and butylbenzene for a zeolitecatalyst promoted with lanthanum at a lanthanum/aluminum atomic ratio atleast equal to a metal/aluminum atomic ratio of the catalyst undertemperature and pressure conditions that are the same.
 9. The process ofclaim 1 further comprising terminating the supply of the aromaticfeedstock and alkylating agent to the reaction zone and thereafterregenerating the metal-promoted zeolite in the reaction zone by aregeneration procedure comprising injecting an oxygen-containing gasinto the reaction zone to provide a regeneration temperature in thereaction zone of between about 500 and about 585° C., and thereafterreinstituting the supply of the aromatic feedstock and alkylating agentin the production of the alkylation product in accordance with claim 1.10. A process for the production of ethylbenzene comprising: providingan alkylation reaction zone containing a catalyst consisting essentiallyof a metal-promoted beta zeolite aromatic alkylation catalyst, where themetal is selected from the group consisting of Atrium and a rare earthof the lanthanide series other than cerium; supplying a feedstockcontaining benzene in an amount of from about 20% to about 90% of thearomatic content and ethylene to the alkylation reaction zone; operatingthe alkylation reaction zone at temperature and pressure conditions inwhich benzene is in a supercritical phase or liquid phase to causeethylation of the benzene in the presence of the promoted zeolitealkylation catalyst to produce an alkylation product comprising amixture of benzene, ethylbenzene, and polyethyl benzene; recovering thealkylation product from the alkylation reaction zone and supplying theproduct from the alkylation reaction zone to a recovery zone for theseparation and recovery of ethylbenzene from the alkylation product andthe separation and recovery of a polyalkylated aromatic componentincluding diethylbenzene; supplying at least a portion of thepolyalkylated aromatic component including diethylbenzene in thepolyalkylated aromatic component to a transalkylation reaction zonecontaining a molecular sieve transalkylation catalyst; supplying benzeneto the transalkylation reaction zone; operating the transalkylationreaction zone under temperature and pressure conditions to causedisproportionation of the polyalkylated aromatic fraction to produce adisproportionation product having a reduced diethylbenzene content andan enhanced ethylbenzene content; and wherein an ion size of the metalaffects molecular traffic in and out of pores of the catalyst andwherein the metal is selected to balance an acidity and the ion size toget optimum results in a catalyst activity and selectivity.
 11. Theprocess of claim 10 where the metal-promoted beta zeolite alkylationcatalyst has a silica alumina mole ratio within a range of from about 50to about
 150. 12. The process of claim 11 where the metal-promoted betazeolite alkylation catalyst has a metal/aluminum atomic ratio is withina range of from about 0.1 to about
 1. 13. The process of claim 10wherein the metal-promoted beta zeolite alkylation catalyst is formedwith a binder selected from the group consisting of silica, alumina, andmixtures thereof.
 14. The process of claim 10 where the alkylation zoneis operated at temperature and pressure conditions to provide a totalby-product yield of propylbenzene and butylbenzene which is less than acorresponding total by-product yield of propylbenzene and butylbenzenefor a zeolite promoted with lanthanum at a lanthanum/aluminum atomicratio at least equal to a metal/aluminum atomic ratio of themetal-promoted zeolite catalyst under temperature and pressureconditions that arc the same.
 15. The process of claim 10 wherein theprocess is applied in a production scale alkylation plant.
 16. Theprocess of claim 10 wherein the metal is yttrium that has an orbitalthat is less full and is more electropositive than cerium.
 17. Theprocess of claim 10 wherein the metal is selected from the lanthanideseries and has a charge that is the same as cerium when ionized, but issmaller and more electropositive.
 18. The process of claim 10 whereinthe metal is neodymium, and is more electropositive than cerium.